In research and development of a high technology related to drug design or the like, needs of a molecular orbital calculation using a computer have been increased. The molecular orbital function is useful for research of photoresponsiveness and reactivity of a molecule to be a development target. Especially, molecular orbitals such as a HOMO (Highest Occupied Molecular Orbital) and a LUMO (Lowest Unoccupied Molecular Orbital) are frequently drawn by a three-dimensional drawing using the computer. In order to draw the molecular orbitals, a molecular orbital drawing program and a molecular orbital drawing apparatus are used. A GUI (Graphical User Interface) for an easy user operation is realized.
However, in the above-described drawing of the molecular orbitals, especially in a case of handling a large scale molecule, a calculation using a large amount of data is performed. In many molecular orbital calculation programs, expansion coefficients of the molecular orbitals acquired from a molecular orbital calculation result are output to a file. By a molecular orbital drawing program, a drawing process is executed. In the drawing process, expansion coefficient data and basis function data are read out from the file and values of molecular orbital functions are calculated. Alternatively, in addition to the file to which the expansion coefficients are output, a result file may be output as a result from actually calculating function values of three-dimensional lattice points. The molecular orbital drawing program may read the result file, and then, the drawing process may be performed.
In a case in which a data amount related to the drawing process is increased, a drawing time may be delayed. In order to improve drawing speed, values of basis functions of the three-dimensional lattice points may be calculated beforehand. Moreover, lattice points themselves may be reduced.